Submetering is the resale of electricity or allocation of costs within a multi-tenant property. Master metered apartments are units of a multi-tenant residential building without individual electric meters; the cost of electricity for each apartment is included in the rent for that apartment. Because tenants of such units typically consume up to 30% more electricity than tenants who pay a separate bill for energy consumed, there is a demand for submetering of such units.
Systems and methods for submetering are known. One such system is disclosed in U.S. Pat. No. 4,783,748, issued Nov. 8, 1988, to Swarztrauber et al. In that system, as disclosed in the patent and as developed through 1999, the submeter (known as a Transmeter®) measures electricity by connecting to the power wires to measure voltage and through current transformers to measure current. The initial Transmeters®, manufactured from 1982 through 1991, processed the voltage and current in digital form to derive the real energy. In a development effort that spanned the period from 1988 through 1992, additional parameters were added. The Transmeters manufactured from 1992 through 1999 calculate from the measured voltage and current additional parameters such as reactive and apparent energy, power factor, total harmonic distortion, peak demand, time-of-use, voltage and current. They also stored the information CMOS ram backed up by battery to maintain an audit trail of key energy information either every day or every 15 minutes. This type of memory storage can suffer data loss through power and battery failure, data corruption due to “fast transients”—a type of interference commonly found on power lines.
The Transmeter® systems manufactured and sold through 1999 collect and deliver information from Transmeters® located in multi-tenant properties. The individual Transmeters® inject signals onto the power distribution lines (a technique known as power line communication, or “PLC”) in the multi-tenant property to a more centrally located device, the Transponder. The Transponder is typically installed at the point of entry of electricity to that property. If the property has more than one electrical service, one Transponder is installed per service. The Transponders are interconnected via an RS-485 network. One of the Transponders connects by modem to a dedicated standard telephone line.
The billing computer is configured to dial any property on command of the operator. The data is processed by standard spreadsheet or database programs to generate bills in either paper or machine-readable format for use by the property management companies.
However, such systems have a number of deficiencies. One deficiency is cost: units that are too costly will not be utilized in areas where the profit margins are too small or there is a relatively high probability of theft. Another deficiency shared by many systems is that the meters communicate with a central billing office via telephone lines, thus requiring additional installation of wires in the building, or at least requiring that telephone lines be located near the power lines.
The submetering market has several requirements that often fail to be met by existing submetering systems. Such requirements include:
(1) stringent metering standards found outside the United States such as those of Industry Canada and the International Electrotechnical Commission (a European standards organization with applicability to most of the world outside of North America). Not only must a submeter meet electrical standards, it must comply with strict mechanical standards as well.
(2) Communication with the submeter is required outside of densely populated urban areas, where electrical distribution transformers are not necessarily located near phone lines.
(3) There is an emerging need of electric utilities to provide on-line metering databases over the Internet. This need also includes providing this information to generation companies or Energy Service Companies (ESCOs) often located very distant from the customer. Such entities require delivery of information not available with standard electro-mechanical meters.
(4) Low-cost, high-volume manufacture.